>> Also the shopping cards have a small chain that attaches to the cart in front of it. You unlock the cart by sliding in a quarter so you can use it while shopping.
I must admit that the first thing I did after observing this new system was to test whether the chain was long enough to "lock" the cart to itself and get the quarter back without returning the cart. Try it for yourself ;)
Spoiler spoiler alert: you can however lock two carts to each other, though it is a bit of work! I never tested more than two, but the geometry of the situation would make it moderately difficult.
Not with the ones I've seen in NL, unless you put one cart on top of the other and turn it upside down. Indeed, that's a bit of work, lifting one cart (or pushing both carts flat on their side).
I must admit that the first thing I did after observing this new system was to test whether the chain was long enough to "lock" the cart to itself and get the quarter back without returning the cart. Try it for yourself ;)